The discovery of a vast number of disease biomarkers, new therapies and the establishment of miniaturized medical systems have opened up new avenues for the prediction, diagnosis and monitoring of treatment of diseases in a point-of-care or other distributed test settings. Point-of-care systems can rapidly deliver test results to medical personnel, other medical professionals and patients. Early diagnosis of a disease or disease progression and monitoring of therapy are often critical for treatment of deadly conditions such as certain cancers and infectious diseases.
Diagnosis and treatment of diseases can take advantage of multiplexed biomarker measurements, which provide additional knowledge of the condition of a patient. For example, when monitoring the effects of a drug, three or more biomarkers can be measured in parallel. Typically, microtiter plates and other similar apparatuses have been used to perform multiplexed separation-based assays. A microtiter plate (for example, a 384 well microtiter plate) can perform a large number of assays in parallel.
In a Point-of-Care (POC) device, the number of assays that can be performed in parallel is often limited by the size of the device and the volume of the sample to be analyzed. In many POC devices, the number assays performed is about 1 to 10. A POC device capable of performing multiplexed assays on a small sample would be desirable.
A shortcoming of many multiplexed POC assay devices is the high cost of manufacturing the components of the device. If the device is disposable, the cost of the components can make the manufacturing of a POC device impractical. Further, for multiplexed POC devices that incorporate all of the necessary reagents onboard of the device, if any one of those reagents exhibit instability, an entire manufactured lot of devices may have to be discarded even if all the other reagents are still usable.
When a customer is interested in customizing a POC device to a particular set of analytes, manufacturers of multiplexed POC assay systems are often confronted with the need to mix and match the assays and reagents of the device. A multiplexed POC assay suitable to each customer can be very expensive, difficult to calibrate, and difficult to maintain quality control.
POC methods have proven to be very valuable in monitoring disease and therapy (for example, blood glucose systems in diabetes therapy, Prothrombin Time measurement in anticoagulant therapy using Warfarin). By measuring multiple markers, it is believed that complex diseases (such as cancer) for which multi-drug therapies are required can be better monitored and controlled.
There exists the need to use multiple sources of information for monitoring the health status or disease condition of individuals as well as treatments of various diseases. Especially important is the measurement of concentrations of several selected analytes (biomarkers, antibodies, gene expression levels, metabolites, therapeutic drug concentrations and the like) over time. To make this process convenient and maximally effective, technologies that enable measurement of any and all needed analytes (of whatever types) using a small blood sample (blood drop obtained by finger-stick) or other suitable sample are particularly valuable. Such technology will ideally be operable by non-technically trained users in distributed test settings, e.g., homes, clinics, doctor's offices, pharmacies, and retail shops. The present invention addresses these issues and allows for one to be able to make such measurements routinely in patient's home or other non-laboratory setting.
There also exists the need to make the greatest use of available samples, particularly in the instance where samples (e.g., blood samples) are limited by sample size. Blood samples are used for the great majority of medical/clinical tests. Blood cells have to be separated from plasma (or serum) prior to most types of analysis since the presence of cells would compromise the assay chemistries. For example, glucose and cholesterol are often measured by color-forming chemistries which would be interfered with by the presence of formed elements, especially red cells, or hemoglobin (from lysed red cells).
Distributed test systems ideally require a small blood sample obtained by fingerstick methods. Such samples may be as small as 20 microliters (uL) (one drop) or less. Larger volume samples (say up to 200 uL) usually cannot be taken by fingerstick methods without repeated, inconvenient (“milking”) of fingers. Alternatively venous samples of several milliliters (mL) can be taken but this requires a medically trained phlebotomist.
It is usually very difficult to perform more than a single assay using small blood sample with 20 uL or less. This is especially so when the blood sample has to be filtered to remove cells and the recovery of usable plasma from such small volumes is inefficient. Typically only about 5 uL or less of plasma can be recovered. Samples as large as 200 uL can be efficiently separated by automated POC systems (Abaxis, Biosite etc.) but this cannot be done routinely unless a technician is available to draw the sample.